The present invention relates generally to subterranean well systems and, more particularly, to well system components that reduce excessive acoustic noise that would otherwise interfere with acoustic telemetry systems.
In subterranean well completions, a metal tubing structure, such as a pipe string, is typically supported from an appropriate metal hanger structure and extends downwardly therefrom through a wellbore portion of the completion which is normally lined with a metal casing. In subsea applications, the hanger will typically rest within a wellhead installation arranged on the seabed floor where one or more blow out preventers are used to instantaneously cut off hydrocarbon production in the event a production problem arises. A marine riser extends upwardly from the wellhead installation to the surface and provides a conduit for the tubing to penetrate the seabed floor and access hydrocarbon reservoirs for production.
During hydrocarbon production, it is often desirable to monitor the state of various downhole well parameters, such as the temperature and pressure within the tubing and external to the tubing in the annulus defined between the tubing and the casing. Many times the desired sensing locations for these well parameters are thousands of feet downhole. Thus, signals indicative of the sensed well parameters must be transmitted upwardly via the tubing over great distances through the wellbore, and also through a lengthy marine riser in subsea applications, to a predetermined signal receiving location.
Various techniques have previously been proposed for generating and transmitting these well parameter signals. One such technique is acoustic telemetry which functions by transmitting data through vibrations propagating in the wall of the tubing. The vibrations are typically generated by an acoustic transmitter mounted on the tubing and propagate along the tubing to an acoustic receiver also mounted on the tubing for conversion to, for example, digital or analog electrical signals.
Acoustic telemetry systems often encounter technical obstacles, however, especially in subsea applications where changing sea conditions can affect accurate acoustic transmission. For example, as the riser shifts in response to changes in the sea currents, the tubing may shift within the riser and the wellhead installation and thereby generate acoustic noise. In extreme conditions, the tubing may even strike the riser and/or wellhead installation. This excessive acoustic noise has the effect of reducing acoustic communication reliability. Attempts to improve acoustic transmission reliability have focused generally on optimizing the acoustic transmission frequencies, clamping mechanisms, and acoustic power/signal strength. Such solutions, however, can be complex and oftentimes costly.